In a HDD, a lubricant is applied to the surface of a magnetic-recording disk for the purpose of suppressing mechanical damage due to collision with a magnetic-recording head. Such a lubricant on a magnetic-recording disk decreases with time. Thus, as is known in the art, a structure for controlling the supply of lubricant within the HDD may be used to supply fresh lubricant to a magnetic-recording disk. Engineers and scientists engaged in HDD manufacturing and development are interested in methods and systems for controlling the supply of lubricant within the HDD that meet the rising demands of the marketplace for increased data-storage capacity, performance, and reliability.